A litany of injuries has kept Sean Lee off the field throughout his Cowboys career.

What he's dealing with now is near the bottom of the list.

"This is one of the more minor things I've dealt with,'' Lee said of the sprained medial collateral ligament in his right knee. "We're just making sure it heals and I can come back and practice right.''

Lee suffered the injury in the first practice with pads of this camp when a teammate rolled into him. He hasn't practiced with the defense since but did a bit of work with special teams during Sunday morning's walk-through.

"It's obviously frustrating, but I've gotten to the point where I'm mature enough to look ahead and not let the frustration mess with my preparation,'' said Lee, who has missed 51 games because of injuries in his NFL career. "I'll continue to look at the practice and the goals ahead of me.''

No firm timetable exists for when Lee will return to practice, but the club will obviously move with caution given his history.

Briefly: Cooper didn't practice Sunday because of a bruised heel. But he was moving around fine during the team's morning walk-through and Garrett indicated the Pro Bowl receiver could return when the team next takes the practice field Tuesday.